1. Field of the Invention
In one aspect, this invention relates to clutches for internal combustion engine cooling systems.
In a further aspect, this invention relates to fan clutches which are temperature controlled.
2. Description of the Prior Art
Fan clutches have been common in automobiles and trucks for many years. Such clutches rotate the fan and draw power only when the temperature of the air passing through the radiator, common to such vehicles, reaches a predetermined level.
One example of a mechanical fan clutch known in the art is shown in U.S. Pat. No. 2,990,045 issued to Root. The device of this patent comprises a driven member mounted on a waterpump shaft and having a drive surface. A second member carrying a fan is mounted on the shaft the second member being mounted to allow relative rotation between the first and second members. A thermally responsive element is provided which when heated will move the second, fan carrying member longitudinally along the axis of the water pump shaft bringing the two members into engagement.
A further mechanical fan clutch arrangement is shown in U.S. Pat. No. 3,103,308 issued to Wolfram. In this device two clutch members adapted to rotate independently are moved longitudinally into engagement along the longitudinal axis of a mounting shaft by the action of a temperature responsive wax motor.
The prior art clutches are basically cone clutches which slip when the clutch is not firmly engaged causing substantial wear. Further, the wax pill motors used heat slowly causing a slow clutch engagement and disengagement which causes further wear on the clutch as the clutch slips during engagement and disengagement. Slipping clutches have a short life, low torque transmission and slow engagement.